A major shortcoming of Receiver Autonomous Integrity Monitoring (RAIM) Fault Detection and Exclusion (FDE) is widely recognized to be it occasional lack of availability, in the sense that the integrity level it can protect in any given situation cannot always be smaller than the required alert limit for a given flight operation. Ever since the RAIM FDE algorithms were developed, accepted and published more than ten years ago, the system availability has been bound, by and large, to the limitations of its monitoring mechanism to be able to detect and exclude a single measurement fault. There have been many studies made on evaluating the system availability, usually on a global basis, and they have considered various assumptions of constellation size, horizon mask angle, and aiding with baro-altitude, inertial, and additional non-GPS satellites, or even with Loran. In all of these studies, however, the basic shortcomings of RAIM FDE remained essentially bound by its theoretical limits. More recently, there has been a proposition that departs from conventional assumptions made in the standard RAIM-FDE by better balancing accuracy and integrity levels. This proposition results in the lowering of the horizontal integrity limit for all satellite measurement geometries, thereby improving system availability in the process.
Accordingly, there is a need for a methodology called Novel Integrity Optimized RAIM (NIORAIM) for accomplishing the balancing of position accuracy with integrity. Further, there is a need for a design that is a NIORAIM amenable to real-time computation.
It would be desirable to provide a system and/or method that provides one or more of these or other advantageous features. Other features and advantages will be made apparent from the present specification. The teachings disclosed extend to those embodiments which fall within the scope of the appended claims, regardless of whether they accomplish one or more of the aforementioned needs.